TW550520B - Method for forming bump effect on 3D object in computer graphics - Google Patents

Abstract

The present invention provides a method for forming bump effect on 3D object in computer graphics, which includes the following steps: first, generating coloring vector for one point on the surface of 3D object; next, determining the displacement coordinates of the point based on the coloring vector; then, establishing the convolutional calculation matrix based on the displacement coordinates; then, calculating the diffuse color value for the point, which equals the difference between the convolutional color value of the neighbored points and the average color value, wherein the average color value is the total average of the RGB color frequency values, and the convolutional color value of neighbored points is the product sum of the average color values of neighbored points and the corresponding coefficients for neighbored points in the convolutional calculation matrix; and, calculating the emboss image value for the point, wherein the RGB color frequency values of the emboss image equal to the product of the diffuse color value is subtracted from the original RGB color frequency values and multiplied with the emboss effect coefficients; thus, repeating these steps to calculate the emboss image value for each point on the surface of 3D object.

Description

550520 [Field of the invention] The present invention relates to a method for forming a concave-convex effect on a 3D object (〇bject) of a computer graphic, and in particular to a method for generating a concave-convex object on a computer graphic using an embossing function The method of bump mapping. [Background of the Invention] In the field of computer graphics, how to make 3D objects in computer graphics have the appearance of texture is a very important subject. Among many techniques, the technique of bump mapping is often applied to this subject to increase the detail of the 3D object surface. The 3D object surface model (modei) of graphics is often established by a plurality of polygons. The technology of bump mapping is to change the normal vector of the endpoints of the polygon to generate light and dark textures. 3D objects can look wrinkled and uneven. However, this technology must calculate the changed method for each point on the surface of the 3D object. For the products that process 3D computer graphics, the technology is more complicated and the processing time is longer. Relatively, the calculation speed is slower. . Another variation is to apply the technique of processing 2d images to the computer graphics processing of 3]), such as the Emboss function technology. And this embossing function technology changes a texture sample and wraps it on the surface of the object; although it is not directly applied to the model of the 3D object, it can still achieve the same visual effect. In this regard, SIGGRAPH (Special Interest Gr〇up 〇n

550520 Description of the invention (2)

(Computer Graphics) introduced the technique of diffuse concave-convex mapping in 1998. This technique first applies a texture sample to the surface of an object in a 3D graphic. This is the first image. The surface of this object is simulated by a plurality of polygons. Next, calculate the normal vector, tangent vector, and complex vector of each endpoint of each polygon. Then, a rotation matrix is generated by using the above three directions, and the light source vector is transformed into a tangent space by the rotation matrix. Then, the component of this converted light source vector in the X-Y plane is regarded as the shift coordinate of its corresponding endpoint, and the endpoint is moved. The displacement coordinates of the points in the polygon are calculated by referring to the displacement coordinates of the endpoints and using the method of internal difference. In this way, the displacement coordinates of each point can be calculated, and a new ° polygon is generated. Repeat the above steps to displace all the polygons to produce a second image. Then, subtract the first image ^ from the image value of the second image to obtain the embossed image. ≫ The above method has the following disadvantages: (1) Discontinuous surface texture is easy to produce: the above method is a tangent vector of the end points to determine its displacement coordinates. However, when the surface of the object is a mother surface f steep Λ Xiao At the surface, Μ varies greatly because of the tangent vector, and when the resulting image is wrapped around the 3D object surface, discontinuities or cross-sections will occur. (2) Miscellaneous: i At each point of the legal system, its displacement coordinates must be calculated, which is more complicated in operation and takes more time.

TO0560F.ptd 550520 5. Description of the invention (3) '--- [Objective and summary of the invention] In view of this, the object of the present invention is to provide a method for forming a concave-convex effect on a computer graphic 3D object (OBject). This method provides faster processing, and can avoid the emergence of cross-sections and spots of embossed (Emboss) images. According to the purpose of the present invention, a method for forming a bump effect on a 3D object of a computer graphic is proposed. This method is applied to a computer graphics 3D object. First, a shading vector is generated for a point on the surface of the 3D object. This coloring vector can be the normal vector of this point = the outer product of the light source vector and the normal vector. Next, a shift coordinate at this point is determined, and the shift coordinate is equal to the product of the vector of the coloring vector on the χγ plane and an embossed radius (Emboss radUs) coefficient. Then, a convolution calculation matrix is established, and the convolution calculation moment has a plurality of matrix coefficient values, and these matrix coefficient values are determined by the displacement seats. Next, calculate one of the diffuse color values at this point. This diffuse color value is equal to the difference between the convolutional color value and the average color value of an adjacent point at this point. 'Average color value' is defined as the average of the sum of the R, G, B color frequency (channel ·) values of this point, and the convolution color value of the adjacent point is defined as the average color value and the convolution of a plurality of neighboring points of this point. Calculate the sum of the product of the corresponding coefficients of these neighboring points in the matrix.胄 Calculate the __Emboss- (Emboss) image value at this point, and the R, G, and 8 color frequency values of this relief image value are respectively equal to the R, G, and B color frequency values at this point minus the diffuse color value and one Product of relief effect coefficient. Repeat the above steps to calculate the relief image value of each point on the 3D object surface.

550520 V. Description of the Invention (4) In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below and described in detail with the accompanying drawings. [Preferred Embodiment] The method for forming bump mapping of a 3D object of a Computer Graphics according to the present invention uses an Emboss function to achieve bump mapping. Effect, so that the 3D object surface of computer graphics has the appearance of three-dimensional space (3D). The principle of the present invention is to process a texture sample according to the characteristics of the 3D object surface to generate a relief image; and then wrap the relief image to the 3D object surface. Among them, the present invention uses a shading vector on the surface of the 3D object to determine the shift coordinate of the embossing function of the image; and the shading vector may be a normal vector on the surface of the 3D object (normai vector) or The outer product of the light source vector and the normal vector. In addition, the present invention further refers to the image values of neighboring points to avoid the disadvantage that the neighboring points in the image have too much color difference and discontinuities. Please refer to FIG. 1, which is a schematic diagram of a computer graphic 100 having a 3D object 101. As shown in Figure 1, computer graphics 100 has a textured 3D object 101. In order to apply the method of the present invention, the surface of the 3D object 101 is cut into polygons (not shown in the figure) of appropriate size, and these polygons are used to represent the surface of the 3D object 101. Please refer to FIG. 2 at the same time, which shows a preferred embodiment according to the present invention.

TW0560F.ptd Page 7 550520 V. Description of the invention (5)

A flowchart of a method for forming a concave-convex effect on a computer graphics 3D object according to an embodiment. In FIG. 2, the method of the present invention firstly performs a point p — a coloring vector on a polygon 103 on the surface of the object 101) at step 200m. This shading vector is used to determine the displacement coordinates of the image relief function, that is, it can determine the shading direction of the image relief. Therefore, in this step, the color direction can be the normal vector N of the p point or the cross product of the light source vector l and the normal vector N of the p point. In the present invention, N in the normal direction of the p point means the normal vector N of the polygon 1 03 where the p point is; that is, at any point on the polygon 103, the normal vector is the polygon 1 0. The normal vector N of 3. Such advantages can speed up the calculation speed of the method of the present invention, and avoid the phenomenon of generating cross-sections (ie discontinuous surfaces). Next, in step 203, the normalization (normaiiZe) coloring vector is normalized to obtain a unit length vector of the coloring vector. Proceed to step 2 0 5. In step 205, one of the p-point displacement coordinates is determined. The displacement coordinate is equal to the product of the vector of the shading vector in the X-Y plane and an embossed radius coefficient. This embossed radius coefficient represents the displacement of the embossed effect of the image or the radius of the embossed effect, and it can be set by the user. Then step 207 is performed. In step 207, a convolution calculation matrix is established, and the convolution calculation matrix is used to calculate the image of different relief effects. The convolution calculation matrix has a plurality of matrix coefficient values, and these matrix coefficient values are determined by the displacement coordinates. For example, the convolution calculation matrix may be a two-dimensional matrix, and the displacement coordinates are, for example, (dOffx, dOffy). Then the coefficients (w00, w01, wl0, wll) of the convolution calculation matrix can be (1-w〇i-wlO-wll,

TW0560F.ptd Page 8 550520 V. Description of the invention (6) (\ d〇ffk \ -dOffx) ^ (d 0 ffy-L ^ o ^ J), (dOffx- \ 4〇fM) * ("mash 1- dOffy), (dOffy-L 犹 ") * (d0ffx- b ring)), and the sum of wOO, w01, wlO, and wll is 1. Next, in step 209, a diffusion color value (dif fuse color) dDif fColor is calculated. The diffusive color value dDif fColor is equal to the difference between the convolution color value dCon of an adjacent point of the p point and an average color value dSum. The average color value of p is the average of the sum of its R, G, and B color frequency (cha η ne 1) values, that is, dSum = (Ir (x, y) + Ig (x, y) + Ib (x, y)) / 3 where I (x, y) is used to represent the image value of p point relative to the point (χ, y) on the texture sample, and Ir, Ig, and lb are the color frequencies of r, G, and b, respectively value. The convolution color value dCon of the neighboring point is equal to the sum of the average color value of the neighboring points of the p point and the coefficient corresponding to the neighboring points in the convolution calculation matrix, that is: dCon _ w00 * dSum00 + w01 * dSum01 + wl〇 * dSumlO + wl1 * dSuml1 where 'dSumi j represents the average color value of points (x-i, y_j). And the diffusion color value (1011 generation, 01 buck = (1 (: 〇11- (1811 „1. The purpose of this step is to avoid the occurrence of excessive color difference between adjacent points in the relief image, which may cause noise or discontinuities). Disadvantage. Then proceed to step 2U to calculate the relief image value I '(x, y) of one of the p points. And the relief image value 丨, ^ "of the R, G, B color frequency values are equal to the original R, G of the point P , B color frequency value minus the diffuse color value dDiffc〇i〇r and a net carving effect coefficient dEmbossAmount product. This relief effect coefficient

550520 V. Description of the Invention (7) " dEmbossAmount is used to adjust the effect of relief coloring. The relief effect coefficient dEmbossAmount can be a light source intensity parameter or a visual depth parameter; the light source intensity parameter is used to reflect the strength of the light source to the relief image value, and the visual ice shallow parameter is used for users to adjust the relief effect by themselves Depth. Both of these parameters can affect the effect of image relief. The relief image value I '(x, y) can be expressed as: I, r (x, y) Ir (x, y) dDiffColor ^ dEmbossAmount I, g (x'y) Ig (x, y)-dDiffColor ^ dEmbossAmount ('y) Ib (x'y)-dDiffCo 1 or * dEmbossAmount Then, in step 213, repeat the above steps to calculate the relief image value of each point on the surface of the 3D object 101 to obtain a relief image (Emb〇ss texture), and then emboss this relief image onto the surface of the object 10i, so as to achieve the effect of bump mapping. [Effects of the Invention] The method for forming a concave-convex effect on a computer disclosed in the above embodiments of the present invention has the following advantages: (3) the shape of the 3D object (1) to avoid the surface texture of the cross section: The points in the same polygon are all calculated by their displacement coordinates. This can avoid the phenomenon of discontinuous sections. (2) Avoiding the occurrence of too much chromatic aberration between adjacent points without salience The method of the present invention refers to the image values of adjacent points to calculate the separation. This can avoid the situation of noisy points. Yu carved shirt, such as

TW0560F.ptd Page 10

550520 V. Description of the invention (8) (3) Fast calculation speed. The method of the present invention does not need to calculate its position coordinates point by point, which can increase the calculation speed. ^ In summary, although the present invention e ^ is not intended to limit the preferred embodiment of the present invention as disclosed above, any person skilled in the art of this invention will not depart from the "t :!" of the present invention. Various modifications and retouching can be made, so it is accurate. Although Qianwei regards the scope of the attached patent as defined by the attached application as TW0560F.ptd Page 11 550520 Simple illustration of the diagram [Simplified description of the diagram] The first picture is shown as a Schematic diagram of computer graphics with 3D objects. Figure 2 shows a flowchart of a method for forming a concave-convex effect on a computer graphics 3D object according to a preferred embodiment of the present invention. [Schematic labeling description] 100: 3D objects Computer Graphics 101: 3D Object 1 0 3: Polygon

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Claims (1)

550520 6. Scope of patent application 1. A method for forming a bump mapping effect on a 3D object of a computer graphic, the method includes: generating a shading vector on a point on the surface of the 3D object;之一 A shift coordinate at this point, which is specialized in the product of the vector of the coloring vector in the χγ plane and an Emboss radius coefficient; establish a convolution calculation matrix, which Has a plurality of matrix coefficient values', and each of the matrix coefficient values is determined by the displacement coordinate; One of the ten different points is a diffuse color value, which is equal to the difference between the convolution color value of an adjacent point of the point and an average color value, where the average color value is r, The average of the sum of G and β color frequencies (channe 1) values, the convolution color value of the neighboring point is equal to the sum of the product of the average color value of the plurality of neighboring points at the point and the corresponding coefficients of the neighboring points in the convolution calculation matrix; 'Why count one of the embossed (Emboss) image values, the R, G, and B color frequency values of the embossed image value are equal to the r, g, and B color frequency values of the point minus the diffuse color value and an embossed effect, respectively. The product of the coefficients; and, repeating the above steps to calculate the relief image value of each point on the surface of the 3D object 0 2 · The method as described in item 1 of the patent application range, wherein the coloring vector is a normal vector of the point. 3. The method according to item 1 of the scope of patent application, wherein the coloring direction is a normal vector of a polygon (Poly gn) where the point is located. 550520 Method, in which one of the normal vectors of the colored polygon is outward, in which the step of determining the displacement coordinates is __ 4 · The quantity as described in item 1 of the scope of patent application is a light source vector and the point is located One product (cross product) 〇5. The method of coloring the vector and determining one of the points as described in item 1 of the patent application scope. The method further includes: normalizing the coloring vector. 6 · The method as described in item 1 of the scope of patent application, wherein the displacement coordinate system is (d0ffx, d0ffy), and the coefficients of the rotation calculation matrix (w0〇, w01, w10, wll) are (iw〇i- wi〇-wii, (“必 刺 —d〇ffx) * (d0 ffy-\ d〇ffy \), (d 0 ffx ~) * (U〇 / jf \ d 0 ffy), (d 0 ffy- y〇j ^ j) ^ (dOffx-)), and the sum of wOO, w01, wlO, and w 11 is i. 7 · The method according to item 1 of the scope of patent application, wherein the relief effect coefficient is one Visual depth parameter 8. The method according to item 1 of the scope of patent application, wherein the relief effect coefficient is a light source intensity parameter. TW0560F.ptd Page 14